The present invention relates to a coke oven battery of the type which can be heated by either lean gas or rich gas by means of vertically-extending heating flues disposed in rows between oven chambers. The vertically-extending flues in each row are formed by midfeaters or header walls in heating chambers and are provided with vertically-extending feed flues which conduct air and/or lean gas to feed flue outlets communicating with the heating flues.
In the past, arrangements such as that shown in U.S. Pat. No. 4,004,983 have been provided wherein a plurality of vertically-spaced feed flue outlets have cross sections which increase or decrease in the vertical direction. These slots are typically transverse slots in prior-art ovens. Transversely-extending slots, however, lead to the formation of relatively "tight" flames with an excessive local evolution of heat and corresponding generation of nitrogen oxides, particularly in the case of rich-gas heating. It is possible for some of the resulting flue gas to be recycled between two adjacent heating flues when employing rich-gas heating in order to obviate temperature peaks. The disadvantage of this procedure, however, is that the quantity of recycled gas can be determined only approximately by means of predetermined orifice configurations. Also, additional energy supplied, for example, by a blower is required to circulate the gas.